The invention relates to magnetic disk data storage apparatus and in particular to such apparatus employing flexible magnetic disks contained in protective envelopes.
Apparatus for recording on only one side of such disks has been in common use. U.S. Pat. No. 3,678,481 issued July 18, 1972, for example, discloses the use of a magnetic disk assembly of this type in which recording takes place on only one side of the disk. A U-shaped carriage assembly embraces the disk, and the carriage has a pressure pad in one leg and a magnetic transducer or head in the other leg; and the pressure pad moves the disk toward the head in order to provide magnetic recording on one side of the disk.
Data storage apparatus employing a magnetic disk assembly of this type has also been proposed in the patent to James F. Elliott et al, U.S. Pat. No. 3,879,757 issued Apr. 22, 1975. The Elliott et al apparatus provides for recording on both sides of a magnetic disk, utilizing a pair of heads which are alternately moved into recording contact with the disk. The construction of this patent includes a recording head which deflects the disk out of planar shape with bending and yielding of the disk taking place at the time of data transfer between head and disk. There may be a rather large dimensional range existing between the disk and head positions (the head may bear into the disk a greater or less amount); and the head to disk compliance and wear characteristics are affected by these dimensional tolerances between heads and disk. In addition, the optimum parameters for these variables in terms of peak compliance and long head-disk life are difficult to determine. Control of the disk location and head-disk contact, due to head penetration, also adds cost to the mechanism.